I could see the Archbishop objecting, but on what grounds would the government object? I can't really see too many ministers objecting to a marriage on the grounds of religion nowadays.

That's what I'm wondering too. The Archbishop would be within his rights to voice concerns, especially if there was the possibility of children being raised in some other faith, but if the government got in on the act I think it would bring the whole matter of an established church into question, which I'm sure neither the church nor the crown would want to see happen.

Thanks so much, I had never heard of these ladies before! So how is William descended from these ladies? Through Prince Philip's descent from the Hessian royals, specifically the husband of Alice, Queen Victoria's daughter? Or is through Alexandra of Denmark, wife of Edward VII?

George II > Mary, who married Friedrich II, Landgrave of Hesse-Cassel > Karl, who married Louise of Denmark > etc

There was very little marital contact between the Hesse-Cassels and the Hesse-Darmstadts. There was, however, a great deal of marital contact between the Hesse-Cassels and the Danish Royal House. At one point Friedrich, Landgrave of Hesse [-Cassel] was the direct heir to the Danish throne until Great Power politics intervened:

George II > Mary > Friedrich of Hesse-Cassel > Wilhelm, who married Princess Charlotte of Denmark > Friedrich, Landgrave of Hesse, who was groomed for the Danish Kingship.

You're referring to the "Farran Exemption" which Iluvbertie has raised in post #18. Wiki has a section on it, here.
Until the Royal Marriages Act is tested or challenged in a court of law it's all theory at this stage.

But he is also a direct descendant of "princesses who have married...into foreign families". This means that he is not a subject of the Act. Now what?

Until such time as it is challenged in court the assumption is that the descent from George II in direct line to the British throne takes precedence over descent from a princess who married into a foreign royal house and then had descendents marry back into the British royal house.

The intent of the law is as important as the wording and the intent is to have the monarch or parliament approve who does marry into the British royal house. As the Hanoverians also are directly descended from George II and also in line to the British throne they also ask consent.

The Norwegians, for instance, who are closer to the British throne than the Hanoverians, don't ask for permission to marry from the British monarch.

But he is also a direct descendant of "princesses who have married...into foreign families". This means that he is not a subject of the Act. Now what?

As pointed out, the intent of the Act was to exempt descendants of a princess who have married into a foreign house (i.e. Princess Maud marrying Prince Charles of Denmark and becoming King & Queen of Norway) from having to seek approval of The Sovereign. It wouldn't make sense for the members of the Norweigan Royal Family who are Maud's descendants to seek The Queen's permission for marriage when they are subject to the will of their monarch in Norway.

For others that are direct descendants of George II, such as the Hanovers in Germany, they still seek permission.

so... do they have a sort of checklist they use before they give him permission to marry..if so whats on it?

As far as I am aware there is no checklist and it is up to the monarch of the day e.g. the Queen mightn't be prepared to give consent for William to marry Kate but William knows that his father will so is waiting (this is an example only and based on absolutely no evidence at all) for his father to become king before seeking permission.

I am sure that there are many parents out there who would like to have to give consent to whomever their descendents marry to prevent someone marrying into the family of whom they disapprove but...only the British monarch has that power in law in Britain any more, if the parties are of age.

The situation with Charles was unique in the sense that he was not only having to tread very carefully with his mother (who remained ambivalent about Camilla), but especially William and Harry. Then there was the problem of The Queen Mother, who made it very clear she was adamantly against any remarriage for Charles to Camilla.

Tony Blair and The Archbishop of Canterbury had already been consulted and given their advice that a marriage would be acceptable, provided the British public was ready to embrace it. After The Queen Mother died and polls continued to show the public was supportive, The Queen gave her consent without question for the future of the monarchy.

What happened when The Prince of Wales married Camilla since he was over 25 at the time?

The Act of Settlement meant that he had two choices:

i) ask The Queen for her consent or
ii) if she said no inform the Privy Council and wait a year to see if there was any legislative opposition.

As The Queen gave her consent there was no need to consider option ii.

What criteria The Queen placed on giving that consent we don't know. We can assume that she sought guidance from the PM and the Archbishop of Canterbury as well as discussed things with her grandsons - who would probably have already discussed the issue with their father and prospective step-mother.

By the time of the announcement all these things had been taken into consideration.

In the end, in legal terms, Charles, as the heir to the throne, sought the permission of the monarch and it was given.

Do you think The Queen Mother was against Prince Charles remarriage to Camilla because she was previously married, or because she was named in his divorce from Princess Diana? The family's background has a very famous history of remarraiges.

back on topic.. has anyone in the family had to give up the trone to marry someone that wasn't approved?

__________________"The pain of spending a week with my brother is well worth it."
– Prince William, on joining Prince Harry for a charity motorcycle ride across South Africa

It's usually a routine matter for The Queen to give her consent. In the case of William or Harry, she would seek advice from The Prime Minister as well since they are next-in-line to the throne.

Let's say one of the princes (I'll pick on Harry) decided to wed an unsuitable girl. Given changing cultural mores, what qualities do you think the Queen and/or PM would say are unacceptable? I'm going to assume we can leave out Catholic girls and confine our discussion to girls who are at least nominally Protestant...

Let's say one of the princes (I'll pick on Harry) decided to wed an unsuitable girl. Given changing cultural mores, what qualities do you think the Queen and/or PM would say are unacceptable? I'm going to assume we can leave out Catholic girls and confine our discussion to girls who are at least nominally Protestant...

I reckon it would have to be pretty drastic, I can't imagine HM would approve of a drug addict, single mother with three children to different fathers with a murder conviction. But such an example is highly unlikley ever to occur.

Do you think The Queen Mother was against Prince Charles remarriage to Camilla because she was previously married, or because she was named in his divorce from Princess Diana? The family's background has a very famous history of remarraiges.

back on topic.. has anyone in the family had to give up the trone to marry someone that wasn't approved?

Yes - Edward VIII.

His choice wasn't approved by parliament.

As for anyone else giving up their place in the succession - as far as I am aware no. I have no doubt that some were denied the right to marry their first choice, but whether they formally asked for permission and thus were actually denied or advised that permission wouldn't be coming (other then Princess Margaret) I don't know.

Do you think The Queen Mother was against Prince Charles remarriage to Camilla because she was previously married, or because she was named in his divorce from Princess Diana? The family's background has a very famous history of remarraiges.

I think it was a little of both. The Queen Mother never forgot the Abdication and greatly resented The Duke of Windsor for marrying a divorcee and giving up the throne.

While she no doubt realized times had changed, she also knew the divorce and subsequent death of Princess Diana had brought the monarchy its greatest threat since 1936. She did not want Charles to court further controversy to the monarchy by insisting on marrying Camilla.